Air propeller blade



V. LOUGHEED AIR PROPELLER BLADE Filed Feb; 10, 19:58 -2 Sheets-Sheet 1 V 'giar logy/bred ATTORNEY I v LOUGHEED AIR PRd PELLER BLADE Filed Feb. 10. 1958 2 Sheets-Shae}.- 2

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Patented Dec. 12, 1939 ammo am racemes. pupa vim; warhead; L-ucketts, vs.

-}; Application February is, loss, Serial No. issnzo 1'3 Claims.

My invention relates to air propellers and more particularly to method and means for making a reinforced air propeller blade oi exceptionally high strength and in which the reinforcingelaments are held securely against slippage and sep aration during operation of the blade at extremely high speeds;

Most of the air propeller blades in commercial today on the larger aircraft are solid blades *made in one piece from some metal alloy such as aluminum or magnesium alloys. These blades are usually unsatisfactory in that they are sublost to failure under high speed operation, such failure almost invariably resulting in serious ac 1 cident'. Experience with these blades, which are chiefly loadedby excessive vibration and enormous centrifugal force, has proved that the most (oi. ire-159) blade is mounted upon and'driven by the shaft from the aircraft motor.

Preferably, the reinforcing material, per, so, used in the present invention, is of the type disclosed in my copending application Serial No.

184,797 filed January 13, 1938. Essentially, this material comprises a web or fabric of interwoven organicfibers and small steel wires so arranged that the wires do not cross each other, the fabric being impregnated with a suitable plastic 'mate- 10 rial, such, for example, as aphenol-formaldehyde resin. For purposes of the present invention, the fabric is used in the form of a braid or tape, as elongated narrow strips. This fabric is being claimed in my co-pending applica- 1 tion and is not claimed per se in the present appiication.

. The tapes or strips ofreinforced material, out to suitable and varied. lengths, which are looped around the anchor rings in accordance with my go trifling scratch on the surface or flaws within the 3 metal tend to develop into a crack which under working conditions results in the whole or a portion of the blade vibrating or flying ofi, thereby so radically imbalancing the revolving propeller and the motor as to cause instant disaster to the aircraft. 7 I n An object of my invention is to provides. reinforced air propeller blade that has unusually high strength and in which the reinforcing members are maintained securely as an intearei part of the blade. n

A further object is to provide a propeller blade at non-homogeneous material, tending to dampen rather than to amplify vibration, and of a compound structure not prone tototal failure from the eflects of partial failure.

In its preferred embodiment, the air propeller blade of my invention is characterized generally by a core of solid plastic material and an outer shell oi laminated rdniorced plastic material firmly bonded to the plastic core. The reinforcing material is in the form of strips or tapes of longitudinal wires and transverse organic filler which are overlapped and bonded tosether to provide a continuous stressed smn for the blade,- and which are ioopm around anchor rings" 10- caM within of the blade to securethe wira from pulling out of the blade root. Obviously, when fastened to such anchor. by being looped around them. there can he hopes? aibility of the reinforcing atripapullins out or becoming separated from the root of the blade. The anchor rings are integrally molded into the root of the blade and when the blade is in use they are clamped in complementary-shaped grooves or sockets within the hub by which the present invention, are suitably arranged as by covering a blade form or "former" with them, and then. this assembly placed in a mold wherein it is subjected to heat and pressure suflicient to.

cause the plastic material. to bond the strips of g5 reinforced material as a substantially homogemeans or unitary body to the blade form. The blade form may be'of the hollow, perforated, or

. porous type disclosed in my copending application Serial No. 1.843% filed January 13, 193$..8il

and a solid core provided in the blade by injection oi molten plastic material into the blade form as disclosed in that application. In that case some of the injected core material permeates the op nin s in the blade form and consoli- 35 dates with the-plastic-impregnated reinforcing strips that cover the blade form, thus providing a strong bond between the core, blade form, and surrounding reinforced material. Alternatively,

the tapes may be grouped and aggregated with 45 out the aid of any form, or they may be arranged-- to form the core of the blade and plastic-material molded around this core. In any case, an essential feature of the structure is the manner in which each tape, and, ac-

oordingly, every individual wire reinforcing the blade, is doubled upon itself to constitute paired reinforcing elements within the blade, which neverthelem are integral with each other and securely anchored tothebladerootbythever m simple and practical but wholly new expedient o being looped, where they are doubled, around as f anchor rings. These rings are molded within the blade root and are made too strong to deform and too large to pull out through holding g5 ferrule or hub element of a controllable, adjustable, or fixed-pitch .propeller, into which the blade must be held with absolute security.

The novel. features of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to organi zation and method of operation will be clearly understood from the following description taken in conjunction with the accompanying drawings, which illustrate the general method of fabricating my improved propeller blades, and in which:

Fig. 1 is a plan view of the completed blade with parts broken away to show the internal structure;

Fig. 2 is a perspective view partly in section illustrating the arrangement of the reinforcing strips around the anchor rings;

Fig. 3 is a sectional view taken along lines 3+3 of Fig. l; I

Fig. 4 is a sectional view taken along lines 4-4 of Fig. 1;

Fig. 5 is a sectional view taken along lines 55 of Fig. 1;

Fig. 6 is a sectional view of a modified type of blade using no blade form;

Fig.7 is a longitudinal sectional view illustrating a typical mounting of my air propeller blade within a standard hub;

Fig. 8 is a perspective view of a modified form of anchor ring and Fig. 9 is a sectional fragmentary view of the anchor ring of Fig. 8 installed in the blade hub.

Referring now to the several figures in the drawings, it will be noted in Fig. 1 that the'blade it comprises a stressedouter skin or shell ll, provided by the aggregated laminated and molded strips of reinforcing material arranged around an inner blade form l2. This form may be made of an expansible metal bag or tube, as disclosed in my copending application Serial No. 184,798, having a plurality of perforations it. A part of the plastic material from the core of the blade flows through these openings l3 and forms a bonding medium indicated at it between the outer reinforcing strips H, the blade form it, and the core of the blade consisting of solid plastic material as indicated at iii.

The strips of reinforced plastic material which form the outer shell H of the completed blade are firmly and securely held in their respective places by means of the anchor rings I 5 and i6 located around and molded into the root of the blade Ill. The reinforcing strips are arranged in the form of hairpin-like loops, with the legs of each thereof preferably of equal length, and placed around these two anchor rings so that they cannot be pulled loose from these rings or from the blade by the high centrifugal forces exerted on them during operation of the blade with high speed motors. The relative sizes of the rings l5 and I8 and the root of the blade Ill are such that these rings cannot slip out through the hub, as is explained more in detail hereinafter.

The preferred arrangement of the reinforcing strips around the anchor rings is more clearly shown in Fig. 2; It will be noted from this figure that each of the reinforcing strips is looped around one or the other of the two anchor rings I 5 and I6, each strip extending from some point on the blade up to and around the anchor ring and back down to the starting point, or to some other desired point on the blade. The number of anchor rings may be varied in accordance with specific requirements of different blade and hub above.

designs, from one to any greater number, and likewise the number and thicknesses of the reinforcing strips of material such asshown at I'l and It in Fig. 2 may be varied. In a common established design, two anchor rings such as shown in Fig. 2 will be used for holding the reinforcing strips, and these rings may be respectively of substantially square and substantially triangular cross section, for example, to conform with the shape of the sockets in one conventional type of air propeller blade hub. It will be understood, however, that my invention is not limited to these forms or any specified number of rings, and that various modifications in the shape, number, size and location of these rings may be made as desired.

Furthermore, these members for anchoring the reinforcing strips, which I have identified as anchor rings, are not necessarily in the form of true rings. They may assume any suitable form of holding element that can be located in and around the root of the blade transverse to the longitudinal axis of the blade, and around which the reinforcing strips can be looped in secure fashion as explained above. For example, a gearlike or toothed form of member, such as shown in Figs. 8 and 9, may be used.

In the sectional views shown in Figs. 3 and 4 it will be'noted that the blade comprises essentially an inner solid core 19 which may be made of any suitable material which will give the blade the proper strength and which will not add unduly to its weight. An advantageous example of'suitable material is a phenol-formaldehyde resin which may be injected into the blade form in unpolymerized condition as described in my copend- .ing application supra, Serial No. 184,798, and

permitted to cool and harden to form the core of the blade. Next surrounding this solid core is the blade form l2. This may be made of any suitable, strong, light-weight, expansible -material such as thin metal sheet, canvas, rubber, etc. The form or former I2 is preferably of a porous nature or is systematically pierced with openings of suitable shapes and sizes to permit penetration of some of the molten material therethrough to form a bonding agent between the core and the outside layer of reinforced material as described However, this is not essential and the form I 2 may be made if desired, of non-porous material, or it even may be omitted. Surrounding the blade form I2 is the outer skin, shell,.or covering consisting of the overlapping, piled-up strips ll of reinforced material. These strips, as shown, are uniformly spaced, lapped, and arranged, but this is not essential and in actual practice it is likely that the strips will bulk rather irregularly, and cross each other at various angles in the completed blade. Insofar as the strength of the blade is concerned, these strips may be piled up into rather random laminations provided only that they constitute a continuous and complete outer covering adequate to confer upon the blade the desired strength.

The sectional view of the blade in Fig. 5 shows the solid inner core I! and the outer reinforcing layer 2| as they may appear near the tip of the blade. This layer 20 here consists of the impregnated ends of the longer loops of tape running out from the anchor rings, most of the loops terminating before they reach so far out along the blade length. It is thus that progressive variation in blade strength and cross-sectional area is provided for, by planning and grouping tape and wire loops of differing lengths, which in the aggregate, as packed and then molded together, give the requisite volumes of wire and plastic at each station along the blade length.

The modified form of blade indicated in the sectional view in Fig. 6 consists of a core of plastic material 2| which is surrounded by the layer of reinforcing material 22. In this modification the blade does not use any blade form.' It could be made by forming the reinforced strips of mal terial around a mandrel in the general form of the final blade, removing this mandrel and placing the hollow member so formed in a mold, followed by injecting into this hollow member the softened 1 it as preferable, that the reinforcement be con- 25- fined to the exterior skin or shell of the blade.

It may, in addition, be used in the blade core,

and it even will serve some useful purpose if provided in the core only and not at the blade surface. In these latter arrangements the strips 30 of reinforcing material may be looped around the anchor members imbedded in. the root of the blade. Y

The illustration in Fig.7 shows how one widely used adjustable hub type afiords a suitable means 86 for mounting a blade made in accordance with this invention on the engine crankshaft or other driving shaft of an aeroplane or other aircraft. As indicated, the blade i0, having a solid core It, a blade form it, and an outer skin or shall so of reinforcing material i i with anchor rings land it located around and molded into the root of the blade, is Inc in a split ortwo piece hub shown generally at 28. The hub halves. separated at 338, are held together and fastened as to the revolving shaft 24 of the engine, not

shown, by means of the locknut assembly indicated at it. The hub halves extend downward v over the root of the blade as indicated at it and are held ly together around the blade so root by means of clamping ring 2?, supplementing the clamping by the shaft 2d and the locknut assembly lit. It will be noted that the extensions 2b of the hub have two sockets complementary in shape to the clamping rings it and 55 it around the root of the blade, with a pro- I v tuberance or inrd shoulder 28 srating these' sockets. The inward shoulder 2d and the outer shoulder as positively prevent the anochorrings I5 and i6 and, therefore, theattached blade id 60 from coming loose from the hub 23. If desired. there may be provided a sleeve-like ferrule 8d molded into the root of the blade as an extra reinforcement to resist crushing of the blade at the root where it is clamped in the hub 23. As has been suggested, it is to be noted that the hub 23 is hollow above the root of the blade it and consists of two halves '3i and 32 which come 'closelytogether at the center as indicated by the 70 dividing lines 83.

. The modified form of anchor ring shown'in Fig. 8 comprises an annular portion 8% and a plurality of tooth-like projections 35. The strips of reinforcing material may be looped over the 75 projections 35 in the manner indicated at 36, and

toothed portions 35 extending into correspondingly shaped channels in thehub as shown 'at to and thereby prevent the blade from pulling out of the hub.

It will be understood that various modifications and changes may be made in the materials and arrangements therefor in the reinforced air propeller blades described above without departing from the scope and spirit of my invention.

I claim: l5 1. In a reinforced air propeller blade containing strips of reinforcing material surrounded by hardened plastic material, an anchor member located at the root of the blade that n anchors-securely as an integral part of the blade "9 strips of reinforcing material looped around said anchor member.

2. In a reinforced air propeller blade containing strips of reinforcing material surrounded by hardened plastic material, an anchor element imbedded in the root of the blade and holding securely as an integral part of the blade a plurality of such strips of reinforced material which are located around the periphery of said anchor element.

3. In a reinforced air propeller blade, an anchor element located within the root of the blade and a plurality of reinforcing filar elements looped around said anchor element said filar elements being imbedded within plastic material and forming a substantially integral part of said blade.

- 4. In a reinforced air propeller blade consisting predontly of laminated moldedstrips of plastic-impregnated web material, a plurality 49 of anchor members imbedded within said web material and located adiacent'the root of the blade, at least some of. said strips being looped around said anchor members and securely held thereby as substantially 'integral parts of the blade.

5. In a reinforced air propeller blade, an anchor ring of substantially square cross section and an anchor ring of substantially triangular cross section imbedded within the root of the 50 blade, and a plurality of elongated strips of re 'iniorcing material composed of interwoven wire and organic fiber threads and impreted with plastic, looped around said anchor rings.

6. In a reinforced air propeller blade containing a plurality of elongated reinforcing ele-- ments surrounded by plastic material, an anchor ring located within the root of the blade and anchoring around the periphery of said ring a plurality of said elongated reinforcing elements so which constitute an integral part of said blade.

7. A reinforced air propeller blade comprising a solid core of plastic material, an expansible blade i'orm surrounding said core, a layer of reinforced" plastic material surrounding said 5 blade form and a plurality of anchor rings molded into the root of the blade and anchoring said layer of reinforced material which is looped around said ring so that the reinforced material will resist slippage- 8. A reinforced air propeller blade comprising a' solid core, an outer shell of reinforcing material surrounding said core and at least one anchor ring located around the root of the blade for securely holding said reinforcing material intact 15 as an integral part of the blade, said reinforcing material comprising elongated doubled strips of various lengths looped around said ring and surrounded by hardened plastic material.

'9. A reinforced air propeller blade comprising a solid core, a plurality of anchor rings surrounding said core near the root of the blade and a plurality of strips of reinforced plastic material looped around said anchor rings in substantially hairpin form and laminated and bonded together to provide a continuous outer reinforced shell for said blade.

10. A reinforced air propeller blade comprising a plurality of anchor rings located around the root of the blade and a plurality of elongated reinforcing strips looped around said anchor rings and bonded together with hardened plastic material to form a continuous reinforced shell for said blade, said strips being composed of a web of interwoven organic fiber threads and fine steel wires so arranged that said steel wires have substantially no contact with one another.

11. A reinforced air propeller blade as defined in claim 1 in which the strips of reinforcing material are of various lengths.

12. A reinforced air propeller blade as defined in claim 1 in which the anchor element is a ring having tooth-like projections with at least some of the strips of reinforcing material looped over said projections.

13. A reinforced air propeller blade comprising an anchor element located around the blade, a plurality of elongated elements of reinforcing material looped around said anchor element and embedded in hardened plastic material as an integral part or said blade.

14. An air propeller blade as defined in claim 13 in which the reinforcing material is composed of 5 a plurality of fine steel wires held in spaced relationship by organic fibers.

15. A reinforced air propeller blade comprising a core of hardened plastic material, a reinforcing covering for said core containing a plurality of 19 elongated reinforcing elements which are looped 15 around said anchor element.

16. An air propeller blade as defined in claim 15 and characterized further by the use of a perforated metal blade former located between the core and outer reinforcing material and bonded thereto by the plastic material as an integral part of the blade.

17. A reinforced air propeller blade comprising a core of hardened plastic material, an

anchor element located around the core, and 95 adapted to hold the blade securely in a blade hub, a relatively large number of fine wires looped around said anchor element and embedded in said plastic core material as a reinforcement therefor,

each of said looped wires being paired into sub- 30 stantially hairpin-like form.

VICTOR LOUGIEWED. 

